Without limiting the scope of the invention, its background is described in connection with methods and compositions used in imaging of geological structures. Geological structures have been characterized using electromagnetic methods; however, the majority of these methods have not utilized injected magnetic materials and have typically relied upon the low conductivity and permittivity of petroleum compared to brine, which is usually found concurrently with petroleum in geological structures. In addition, when injected magnetic materials have been used, the high salinities and elevated temperatures of the subsurface reservoirs result in aggregation of the magnetic materials and their adsorption (i.e., the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface) on mineral surfaces in the subsurface reservoirs. Although, polymer stabilizers have been used they have not provided sufficient electrostatic repulsion and/or are ineffective under the conditions present in the subsurface reservoirs. For example, U.S. Patent Publication Number 2009/0179649, entitled “Methods for Magnetic Imaging of Geological Structures,” discloses methods for imaging geological structures including injecting magnetic materials into the geological structures, placing at least one magnetic probe in a proximity to the geological structures, generating a magnetic field in the geological structures, and detecting a magnetic signal. At least one magnetic probe may be on the surface of the geological structures or reside within the geological structures. The methods also include injecting magnetic materials into the geological structures, placing at least one magnetic detector in the geological structures, and measuring a resonant frequency in at least one magnetic detector. Methods for using magnetic materials in dipole-dipole, dipole-loop and loop-loop transmitter-receiver configurations for geological structure electromagnetic imaging techniques are also disclosed.
U.S. Pat. No. 4,291,271, entitled “Method for Determining Pore Size Distribution and Fluid Distribution in Porous Media,” discloses determining the pore size distribution and the distribution of fluid in a porous media, such as a reservoir rock formation, by nuclear magnetic resonance spectrometry techniques. A sequence of three radio frequency pulses is applied to a sample which is placed in a large static magnetic field, and the resultant spin echo is measured and utilized to determine the pore size distribution in the porous media. If water is present in the sample, the sample is doped so as to substantially eliminate the nuclear magnetic resonance response of the hydrogen in water. The technique can be utilized to distinguish between hydrocarbon filled and water filled pores in the sample, thus providing information concerning the fluid distribution in the sample.